In the disc drive for playing high-density optical discs such as CD players, DVD players, CD-ROM drives or DVD-ROM drives, it is necessary to adjust the direction of the optical axis of the optical pickup to intersect at the right angle the disc surface (skew adjustment) in the assembly process. As the skew adjustment, the following methods have been conventionally performed.
FIG. 23 shows the skew adjustment by adjusting the heights of three fulcrums among four fulcrums which are rotatably mounted on a chassis for supporting respective ends of two guide rods 102, 102 for guiding the optical pickup 101 along a disc surface. The height of each fulcrum is adjusted by rotating the fulcrum itself so that a helical cam 103 defined on the fulcrum lifts up or down its associated end of the guide rod 102.
FIG. 24 shows another conventional skew adjustment in which three portions of a motor base supporting a motor 104 are adjusted their heights by screws 105.
The skew adjustment is comprised of a tangential skew adjustment and a radial skew adjustment. The tangential skew adjustment adjusts the optical axis of the optical pickup to intersect at the right angle the disc surface, seen from the direction of a trace of the beam spots of the optical pickup, i.e., a normal on the disc surface. The radial skew adjustment adjusts the optical axis of the optical pickup to intersect at the right angle the normal line, seen from the direction intersecting at the right angle the disc surface.
The conventional skew adjustments as shown in FIGS. 21 and 22 have a following. For example, in the former one (FIG. 21), i.e., the skew adjustment by adjusting the attitude of optical pickup, the adjustment at each end of guide rods badly influences with each other. That is, since it is impossible to independently perform the tangential skew adjustment and the radial skew adjustment, there is required a lot of times and labors for completing the skew adjustment. Because the tangential skew adjustment deteriorates the formerly completed result of the radial skew adjustment, and vice versa. The latter one (FIG. 22), i.e., the skew adjustment by adjusting the attitude of motor also has a similar problem.